Hybrid automatic repeat request timing for reduced transmission time intervals

ABSTRACT

Systems, methods, and apparatuses are described for wireless communication, including for hybrid automatic repeat request (HARQ) feedback in a system that supports communications using transmission time intervals (TTIs) of different durations. A base station may identify a user equipment&#39;s (UE) capability to provide HARQ feedback for transmissions that use TTIs of a shorter duration relative to other TTIs supported in the system. The base station may select a HARQ timing mode based on the capability of the UE and may indicate the selected HARQ timing mode to the UE. The base station may then transmit one or more data transmissions to the UE using the reduced TTIs. The UE may respond with HARQ feedback based on the HARQ timing mode. The HARQ timing mode may be based on different response times based on the location of the data transmission within a TTI or relative to data transmission in other TTIs.

CROSS REFERENCES

The present Application for patent claims priority to U.S. ProvisionalPatent Application No. 62/315,601, entitled “Hybrid Automatic RepeatRequest Timing For Reduced Transmission Time Intervals,” filed Mar. 30,2016, assigned to the assignee hereof.

BACKGROUND

The following relates generally to wireless communication and morespecifically to hybrid automatic repeat request (HARQ) timing forreduced transmission time intervals (TTIs).

Wireless communications systems are widely deployed to provide varioustypes of communication content such as voice, video, packet data,messaging, broadcast, and so on. These systems may be capable ofsupporting communication with multiple users by sharing the availablesystem resources (e.g., time, frequency, and power). Examples of suchmultiple-access systems include code division multiple access (CDMA)systems, time division multiple access (TDMA) systems, frequencydivision multiple access (FDMA) systems, and orthogonal frequencydivision multiple access (OFDMA) systems. A wireless multiple-accesscommunications system may include a number of base stations, eachsimultaneously supporting communication for multiple communicationdevices, which may each be referred to as a user equipment (UE).

Wireless multiple-access technologies have been adopted in varioustelecommunication standards to provide a common protocol that enabledifferent wireless devices to communicate on a municipal, national,regional, and even global level. An example telecommunication standardis Long Term Evolution (LTE). LTE is designed to improve spectralefficiency, lower costs, improve services, make use of new spectrum, andbetter integrate with other open standards. LTE may use OFDMA on thedownlink (DL), single-carrier frequency division multiple access(SC-FDMA) on the uplink (UL), and multiple-input multiple-output (MIMO)antenna technology.

In an LTE system, a UE may transmit HARQ feedback information tofacilitate error correction and data transmission. HARQ processingprocedures may, however, create delays between reception of downlinkinformation and HARQ feedback transmission. These delays may result inincreased latency and a decrease in overall system performance. CertainHARQ procedures also may not account for communications that use TTIs ofdifferent durations.

SUMMARY

A base station may identify a user equipment's (UE's) capability toprovide hybrid automatic repeat request (HARQ) for low latencytransmissions. The base station may select a HARQ timing mode based onthe capability of the UE, and the base station may indicate the selectedHARQ timing mode to the UE. The base station may transmit one or morelow latency transmissions to UE using TTIs of a reduced durationrelative to other TTIs supported by a system. The UE may respond withHARQ feedback based on the HARQ timing mode. In some cases, the HARQtiming mode may have different response times, which may be based on thelocation of the data transmission relative to other transmissions.

A method of wireless communication in a system that supportstransmission time intervals (TTIs) of a first duration and a secondduration that is less than the first duration is described. The methodmay include determining a hybrid automatic repeat request (HARQ) timingmode based at least in part on one or more capabilities of a UE toprovide HARQ feedback in response to communications using transmissiontime intervals (TTIs) of the second duration and communicating using theHARQ timing mode.

An apparatus for wireless communication in a system that supportstransmission time intervals (TTIs) of a first duration and a secondduration that is less than the first duration is described. Theapparatus may include means for determining a HARQ timing mode based atleast in part on one or more capabilities of a UE to provide HARQfeedback in response to communications using TTIs of the second durationand means for communicating using the HARQ timing mode.

A further apparatus for wireless communication in a system that supportstransmission time intervals (TTIs) of a first duration and a secondduration that is less than the first duration is described. Theapparatus may include a processor, memory in electronic communicationwith the processor, and instructions stored in the memory. Theinstructions may be operable to cause the processor to determine a HARQtiming mode based at least in part on one or more capabilities of a UEto provide HARQ feedback in response to communications using TTIs of thesecond duration and communicate using the HARQ timing mode.

A non-transitory computer-readable medium storing code for wirelesscommunication in a system that supports transmission time intervals(TTIs) of a first duration and a second duration that is less than thefirst duration is described. The non-transitory computer-readable mediummay include instructions to cause a processor to determine a HARQ timingmode based on one or more capabilities of a UE to provide HARQ feedbackin response to communications using TTIs of the second duration andcommunicate using the HARQ timing mode.

A non-transitory computer readable medium for wireless communication isdescribed. The non-transitory computer-readable medium may includeinstructions to cause a processor to determine a HARQ timing mode basedon one or more capabilities of a UE to provide HARQ feedback in responseto communications using TTIs of the second duration and communicateusing the HARQ timing mode.

Some examples of the methods, apparatus and computer readable mediadescribed herein include features of, means for, or instructions forreceiving a first transport block (TB) during a first TTI and a secondTB during a second TTI, where the first TTI and the second TTI each havethe second duration, and identifying a feedback time period based atleast in part on the HARQ timing mode, where the HARQ timing mode mayinclude a first HARQ response time and a second HARQ response time thatis less than the first HARQ response time, and transmitting one or moreHARQ feedback messages associated with the first or the second TB duringthe feedback time period, where the one or more HARQ feedback messagesare received during a TTI of the first duration.

In some examples, communicating includes receiving a first transportblock (TB) during a first TTI and a second TB during a second TTI, wherethe first TTI and the second TTI each have the second duration,identifying a feedback time period based at least in part on the HARQtiming mode, where the HARQ timing mode comprises a first HARQ responsetime and a second HARQ response time that is equal to the first HARQresponse time, and transmitting one or more HARQ feedback messagesassociated with the first or the second TB during the feedback timeperiod, where the one or more HARQ feedback messages are received duringa TTI of the first duration. In some examples, the first TTI is within alatter part of a first time period having the first duration and thesecond TTI is within an initial part of a second time period having thefirst duration. Additionally or alternatively, the one or more HARQfeedback messages may include a first HARQ feedback message and a secondHARQ feedback message distinct from the first HARQ feedback message.

In some examples, a latter portion of the first HARQ feedback messageand an initial portion of the second HARQ feedback message aremultiplexed using at least one of a physical uplink control channel(PUCCH) format capable of carrying more than two bits, a division ofbits between the latter portion of the first HARQ feedback message andthe initial portion of the second HARQ feedback message, joint coding ofone or more bits of the first HARQ feedback message and the second HARQfeedback message, or a combination of bits based at least in part on anorthogonal cover code (OCC) and at least one parity bit, or anycombination thereof.

Some examples of the methods, apparatus and computer readable mediadescribed herein include features of, means for, or instructions fortransmitting an indication of the one or more capabilities of the UE toa base station. Some examples of the methods, apparatus and computerreadable media described herein include features of, means for, orinstructions for receiving an indication of a set of HARQ timing modesfrom a base station, and transmitting a HARQ timing mode request inresponse to the indication, wherein the HARQ timing mode is selectedfrom the set of HARQ timing modes based at least in part on the HARQtiming mode request.

Some examples of the methods, apparatus and computer readable mediadescribed herein include features of, means for, or instructions fortransmitting a first transport block (TB) during a first TTI and asecond TB during a second TTI, where the first TTI and the second TTIeach have the second duration, identifying a feedback time period basedat least in part on the HARQ timing mode, where the HARQ timing modecomprises a first HARQ response time and a second HARQ response timethat is less than the first HARQ response time, and receiving one ormore HARQ feedback messages associated with the first or the second TBduring the feedback time period, where the one or more HARQ feedbackmessages are received during a TTI of the first duration.

Some examples of the methods, apparatus and computer readable mediadescribed herein include features of, means for, or instructions fortransmitting a first transport block (TB) during a first TTI and asecond TB during a second TTI, where the first TTI and the second TTIeach have the second duration, identifying a feedback time period basedat least in part on the HARQ timing mode, wherein the HARQ timing modecomprises a first HARQ response time and a second HARQ response timethat is equal to the first HARQ response time, and receiving one or moreHARQ feedback messages associated with the first or the second TB duringthe feedback time period, where the one or more HARQ feedback messagesare received during a TTI of the first duration.

Some examples of the methods, apparatus and computer readable mediadescribed herein include features of, means for, or instructions foridentifying an uplink (UL) control configuration based at least in parton the HARQ timing mode, and transmitting an indication of the ULcontrol configuration to the UE.

Some examples of the methods, apparatus and computer readable mediadescribed herein include features of, means for, or instructions foridentifying a first physical uplink control channel (PUCCH) resourceoffset for UL transmissions that use TTIs of the first duration and asecond PUCCH resource offset for UL transmissions that use TTIs of thesecond duration. In some examples, the second PUCCH resource offset isidentified based at least in part on the first PUCCH resource offset anda delta value. In some examples, the first PUCCH resource offset or thesecond PUCCH resource offset is identified based at least in part on aPUCCH format. The one or more resource sets for UL transmissions may beassociated with each PUCCH format of a set of PUCCH formats, and wherethe one or more resource sets may each associated with a different basestation or layer three configuration.

Some examples of the methods, apparatus and computer readable mediadescribed herein include features of, means for, or instructions foridentifying a first scheduled downlink (DL) transmission indicatorassociated with TTIs of the first duration and a second scheduled DLtransmission indicator associated with TTIs of the second duration. Insome examples, the first duration is a duration of one subframe and thesecond duration is a duration of one slot of a subframe.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates an example of a wireless communications system thatsupports hybrid automatic repeat request (HARQ) timing for reducedtransmission time intervals (TTIs) in accordance with aspects of thepresent disclosure;

FIG. 2 illustrates an example of a wireless communications system thatsupports HARQ timing for reduced TTIs in accordance with aspects of thepresent disclosure;

FIG. 3 illustrates an example of a carrier configuration that supportsHARQ timing for reduced TTIs in accordance with aspects of the presentdisclosure;

FIG. 4 illustrates an example of a carrier configuration that supportsHARQ timing for reduced TTIs in accordance with aspects of the presentdisclosure;

FIG. 5 illustrates an example of a carrier configuration that supportsHARQ timing for reduced TTIs in accordance with aspects of the presentdisclosure;

FIG. 6 illustrates an example of a slot configuration that supports HARQtiming for reduced TTIs in accordance with aspects of the presentdisclosure;

FIG. 7 illustrates an example of a carrier configuration that supportsHARQ timing for reduced TTIs in accordance with aspects of the presentdisclosure;

FIG. 8 illustrates an example of a process flow in a system thatsupports HARQ timing for reduced TTIs in accordance with aspects of thepresent disclosure;

FIGS. 9 through 11 show block diagrams of a wireless device or devicesthat support HARQ timing for reduced TTIs in accordance with aspects ofthe present disclosure;

FIG. 12 illustrates a block diagram of a system including a UE thatsupports HARQ timing for reduced TTIs in accordance with aspects of thepresent disclosure;

FIG. 13 illustrates a block diagram of a system including a base stationthat supports HARQ timing for reduced TTIs in accordance with aspects ofthe present disclosure; and

FIGS. 14 through 19 illustrate methods for HARQ timing for reduced TTIsin accordance with aspects of the present disclosure.

DETAILED DESCRIPTION

Some wireless systems may support multiple transmission time interval(TTI) durations and may use different TTI durations for uplink (UL) anddownlink (DL) transmissions. For example, a base station may transmit DLdata transmissions using a reduced TTI (e.g., a low latency TTI such asa slot-based TTI with a duration of 0.5 ms) and a user equipment (UE)may respond with hybrid automatic repeat request (HARQ) feedback orother UL control information using a control message in a TTI of adifferent (e.g., longer) duration. For instance, a UE may provide HARQfeedback using a legacy or non-low latency UL transmission (e.g., a TTIwith a duration of a Long Term Evolution (LTE) subframe (i.e., 1 ms)).

Using low latency DL transmissions (e.g., TTIs with a duration of 0.5ms) may enable a reduced HARQ retransmission time relative to otherconfigurations, but the latency benefit and efficiency of a HARQresponse may depend on UE capabilities. Thus, a base station mayidentify a UE capability and select a HARQ timing mode accordingly. TheHARQ timing mode may include a reduced response time between a DLtransmission and the associated HARQ feedback, relative to other HARQtiming modes. In some cases, the response time may be differentdepending on the location of the DL transmission. For example, if aslot-duration TTI (or “slot TTI”) is used for the DL transmission, eachtransport block (TB) of the DL transmission may be sent using either thefirst slot or the second slot in a subframe. The HARQ response time forTBs sent in one slot may be different than the response time for TBssent in the other slot.

By way of example, transmission of low latency physical downlink sharedchannel (PDSCH) (e.g., a PDSCH transmission mapped to a slot-durationTTI) may allow for a HARQ timing to be shortened to a 2-slot gap or a3-slot gap, relative to a PDSCH transmission that occupies a subframe.This may allow for a HARQ retransmission round trip time (RTT) of 4 ms,which represents a reduced latency relative legacy LTE operation (e.g.,systems operating according to earlier releases of LTE HARQ may have an8 ms RTT, which may be used for non-low latency transmission). In someexamples, HARQ timing may be shortened to a 3-slot gap or a 4-slot gap,which may allow for a HARQ RTT of 5 ms. In another example, and asdescribed in further detail below, the response time may be the sameregardless of the TTI used for DL transmission, such that the UL controltransmissions are offset in time (i.e., two overlapping subframe lengthUL control transmissions). In another example, HARQ timing for a DL-slotmay align with 1 ms-duration UL control message (e.g., ACK/NACK)transmission timing, but the HARQ RTT may be 6 ms, a reduction relativeto legacy operation.

Aspects of the disclosure introduced above are described below in thecontext of a wireless communication system. Additional examples of thedisclosure are described with reference to configurations of uplink anddownlink channels for low latency HARQ feedback timing. Aspects of thedisclosure are further illustrated by and described with reference toapparatus diagrams, system diagrams, and flowcharts that relate to HARQtiming for reduced TTIs.

As used herein, the terms “low latency” and “reduced latency” may referto timing between transmissions (e.g., RTT) that is less than a similaroperation according to a legacy system or legacy version of a standard.Also, as used herein, “legacy” may refer to an earlier communicationtechnology or release of LTE, which may have timing and operation knownto those skilled in the art, but which does not include the reducedlatency features described herein. In some examples, the term “non-lowlatency” may be used to describe legacy operation in a system thatsupports both legacy and low or reduced latency operation—e.g., in asystem that supports communications using TTIs of different durations.

FIG. 1 illustrates an example of a wireless communications system 100 inaccordance with various aspects of the present disclosure. The wirelesscommunications system 100 includes base stations 105, UEs 115, and acore network 130. In some examples, the wireless communications system100 may be a Long Term Evolution (LTE)/LTE-Advanced (LTE-A) network. Insome examples, wireless communications system 100 may support variousHARQ timing modes, including modes that provide for reduced RTT relativeto legacy HARQ procedures.

Base stations 105 may wirelessly communicate with UEs 115 via one ormore base station antennas. Each base station 105 may providecommunication coverage for a respective geographic coverage area 110.Communication links 125 shown in wireless communications system 100 mayinclude UL transmissions from a UE 115 to a base station 105, or DLtransmissions, from a base station 105 to a UE 115. UEs 115 may bedispersed throughout the wireless communications system 100, and each UE115 may be stationary or mobile. A UE 115 may also be referred to as amobile station, a subscriber station, a remote unit, a wireless device,an access terminal (AT), a handset, a user agent, a client, or liketerminology. A UE 115 may also be a cellular phone, a wireless modem, ahandheld device, a personal computer, a tablet, a personal electronicdevice, a machine type communication (MTC) device, etc.

Base stations 105 may communicate with the core network 130 and with oneanother. For example, base stations 105 may interface with the corenetwork 130 through backhaul links 132 (e.g., S1, etc.). Base stations105 may communicate with one another over backhaul links 134 (e.g., X2,etc.) either directly or indirectly (e.g., through core network 130).Base stations 105 may perform radio configuration and scheduling forcommunication with UEs 115 or may operate under the control of a basestation controller (not shown). In some examples, base stations 105 maybe macro cells, small cells, hot spots, or the like. Base stations 105may also be referred to as eNodeBs (eNBs) 105.

Time intervals in LTE may be expressed in multiples of a basic time unit(e.g., the sampling period, T_(s)=1/30,720,000 seconds). Time resourcesmay be organized according to radio frames of length of 10 ms(T_(f)=307200T_(s)), which may be identified by a system frame number(SFN) ranging from 0 to 1023. Each frame may include ten 1 ms subframesnumbered from 0 to 9. A subframe may be further divided into two 0.5 msslots, each of which contains 6 or 7 modulation symbol periods(depending on the length of the cyclic prefix (CP) prepended to eachsymbol). Excluding the CP, each symbol contains 2048 sample periods.

In some cases, the subframe may be the smallest scheduling unit, alsoknown as a TTI. In other cases, a TTI may be shorter than a subframe ormay be dynamically selected (e.g., in short TTI bursts or in selectedcomponent carriers (CCs) using short TTIs). System 100 may supportcommunications according to TTIs of different durations (e.g., 1 ms and0.5 ms). In some cases, the TTI duration used for UL transmissions maybe different from that used for DL transmissions. For example, a oneslot (0.5 ms) TTI may be used for DL transmissions and one subframe (1ms) TTI may be used for UL transmissions. A 1 ms subframe may bereferred to as an LTE subframe, LTE TTI, or legacy TTI.

Hybrid automatic repeat request (HARQ) may be a method of ensuring thatdata is received correctly over a wireless communication link 125. HARQmay include a combination of error detection (e.g., using a CRC),forward error correction (FEC), and retransmission (e.g., automaticrepeat request (ARQ)). HARQ may improve throughput at the medium accesscontrol (MAC) layer in poor radio conditions (e.g., signal-to-noiseconditions). In Incremental Redundancy HARQ, incorrectly received datamay be stored in a buffer and combined with subsequent transmissions toimprove the overall likelihood of successfully decoding the data. Insome cases, redundancy bits are added to each message prior totransmission. This may be useful in poor conditions. In other cases,redundancy bits are not added to each transmission, but areretransmitted after the transmitter of the original message receives anegative acknowledgement (NACK) indicating a failed attempt to decodethe information. The chain of transmission, response and retransmissionmay be referred to as a HARQ process. In some cases, a limited number ofHARQ processes may be used for a given communication link 125. In somecases, HARQ timing may be different for low latency and non-low latencycommunications. In some cases, when using low latency HARQ, the numberof HARQ processes may be increased (e.g., from a limit of 8 to 10 ormore).

In some examples, wireless communications system 100 may utilizeenhanced component carriers (eCCs). An eCC may be characterized by oneor more features including: wider bandwidth, shorter symbol duration,shorter TTIs (e.g., 0.5 ms TTIs), or a modified control channelconfiguration. In some cases, an eCC may be associated with a carrieraggregation (CA) configuration or a dual connectivity configuration(e.g., when multiple serving cells have a suboptimal or non-idealbackhaul link). An eCC may also be configured for use in unlicensedspectrum or shared spectrum (where more than one operator is allowed touse the spectrum). An eCC characterized by wide bandwidth may includeone or more segments that may be utilized by UEs 115 that are notcapable of monitoring the whole bandwidth or prefer to use a limitedbandwidth (e.g., to conserve power).

In some cases, one or several CCs, such as an eCC, in system 100 mayutilize a different symbol duration than other CCs, which may includeuse of a reduced symbol duration as compared with symbol durations ofthe other CCs. A shorter symbol duration may be associated withincreased subcarrier spacing. A device, such as a UE 115 or base station105, utilizing eCCs may transmit wideband signals (e.g., 20, 40, 60, 80MHz, etc.) at reduced symbol durations (e.g., 16.67 microseconds). A TTIin eCC may consist of one or multiple symbols. In some cases, the TTIduration (that is, the number of symbols in a TTI) may be variable.

A base station 105 may identify a UE capability to provide HARQ for lowlatency transmissions (e.g., TTIs of a reduced duration relative toother TTIs supported by system 100). The base station may select a HARQtiming mode based on the capability and indicate the selected HARQtiming mode to the UE 115. The base station may then transmit one ormore low latency data transmissions to UE 115, and the UE may respondwith HARQ feedback based on the HARQ timing mode. In some cases, theHARQ timing mode may be based on different response times based on thelocation of the data transmission. In other cases, the response timesmay be the same.

FIG. 2 illustrates an example of a wireless communications system 200for HARQ timing for reduced TTIs. Wireless communications system 200 mayinclude base station 105-a and UE 115-a, which may be examples of thecorresponding devices described with reference to FIG. 1. In someexamples, wireless communications system 200 may support various HARQtiming modes, including modes that provide for reduce RTT relative tolegacy HARQ procedures.

In some systems, DL and UL transmission may have different TTI durations(e.g., a 0.5 ms duration for DL and a 1 ms duration for UL). Forexample, a physical uplink control channel (PUCCH) or a physical uplinkshared channel (PUSCH), or both, may be based on the longer UL TTI 205and may be used together with DL transmissions using the shorter DL TTI210. In some cases, a single control channel (e.g., a physical downlinkcontrol channel (PDCCH)) may schedule multiple DL transmissions with thereduced TTI duration (e.g., two slot-TTI transmissions during a subframemay be scheduled together). Alternatively, each reduced TTI transmissionmay be scheduled by a different control channel.

A shorter scheduled downlink TTI may enable reduced UL HARQ timing and,subsequently, the round-trip time (RTT) for the retransmission oftransport blocks (TBs). Additionally, with a shortened TTI duration, TBsscheduled in different TTIs may have different UL HARQ timing tofacilitate common UL HARQ configurations for DL transmissions withdifferent TTIs.

In some examples, a HARQ timing mode may be selected to accommodate twodifferent response DL transmissions occurring at different times. Forexample, transmission of low latency PDSCH, such as a PDSCH using a lowlatency TTI, may allow for a HARQ timing to be shortened to a 2-slot gapor a 3-slot gap, which may allow for a HARQ retransmission round triptime (RTT) of 4 ms. In another example, HARQ timing may be shortened toa 3-slot gap or a 4-slot gap, which may allow for a HARQ RTT of 0.5 ms.In another example, the response time may be the same regardless of thetransmission time, such that the UL control transmissions are offset intime (i.e., two overlapping subframe length UL control transmissions).In yet another example, HARQ timing for a DL-slot may align with 1 msACK/NACK transmission timing, but the low latency HARQ RTT may bereduced to 6 ms. These examples illustrate configurations based onslot-length TTIs and 1 ms subframe length TTIs. But other TTIs may alsobe employed to provide for low latency benefits described herein.

As described above, using a combination of 2-slot and 3-slot timing forHARQ responses may result in 4 ms retransmission RTT. For example, a TBtransmitted in a first slot of a subframe (e.g., slot 0) may have 3-slotHARQ timing. A second slot (e.g., slot 1) may have a two-slot HARQtiming. In this example, PUCCH resources in each subframe for 1 ms TTIUL transmissions may be determined by a control channel four subframesprior, while PUCCH resources for slot length TTI may be determined by acontrol channel two subframes prior.

In another example, using a combination of 3-slot and 4-slot timing mayresult in a HARQ RTT of 5 ms. In some examples using this configuration,DL timing may not align with a subframe boundary (although UL may bealigned). That is, a first TB may be transmitted in the latter part ofone subframe, and a second TB may be transmitted in the first part ofthe next subframe. In such cases, a PUCCH in subframe n may carry HARQfor a second slot (e.g., slot 1) in subframe n−3, and for the first slot(e.g., slot 0) in subframe n−2. That is, a first slot (e.g., slot 1 ofthe first DL subframe) may have a 4-slot HARQ timing. A second slot(e.g., slot 0 of the second DL subframe) may have a 3-slot HARQ timing.

In some examples, DL TBs transmitted in different slots may have thesame HARQ response timing, which may result in staggered PUCCHresponses. For example, a 3-slot HARQ timing with staggered PUCCH mayresult in a 4 ms HARQ RTT. In some cases, each slot length TTI may beassociated with a different 1 ms TTI PUCCH. If back-to-back slot-TTItransmissions occur, the PUCCH for the two consecutive slot-TTItransmissions may result in parallel PUCCH transmissions (at leastduring one overlapping slot length period) or modified PUCCHtransmissions (e.g., transmissions that are multiplexed over anoverlapping slot length period). As an example, for a slot 0 PDSCH insubframe n, PUCCH may be transmitted in subframe n+2; for the lowlatency PDSCH transmitted in the second slot (i.e., slot 1) in the samesubframe n, the PUCCH may be transmitted in slot 1 of subframe n+2 andslot 0 in subframe n+3.

In another example, using a combination of 7-slot and 8-slot responsetiming may result in a retransmission RTT of 6 ms. In such cases, PUCCHfor slot based DL transmission may be aligned with PUCCH transmissionsof 1 ms based DL transmissions occurring at the same time. However, theretransmission time for the low latency DL transmissions may be reducedrelative to legacy operation (e.g., from 8 ms to 6 ms) by reducing thetime period between the PUCCH and the subsequent retransmission.

Low latency HARQ scheduling techniques, including those described hereinmay reduce the possibility of PUCCH resource collision. That is,collisions may result from using different HARQ response timing for lowlatency and non-low latency DL transmissions together. For example, thecollision possibility may be from PUCCH transmission in subframe n,which corresponds to DL transmissions in subframe n−k₁ for 1 ms TTI, andDL transmissions in subframe n−k₂ for slot length TTI. E.g., k₁=4, k₂=2.Since generally, k₁>k₂, it may be possible for base station to avoid orminimize PUCCH resource collision by scheduling slot length TTIsappropriately. For example, the starting PUCCH resource offset may beconfigured separately for 1 ms and 1-slot. The base station 105-a mayuse two different offsets for the two TTIs, such that two differentPUCCH resource pools can be created.

Alternatively, for the slot length TTI, another offset may be introducedon top of the offset configured for 1 ms. That is, if a first offset,Δ₁, is for 1 ms, then a second offset, Δ₁+Δ₂, may be used for 1-slot.The resource offset may depend on a PUCCH format—e.g., one resourceoffset separately configured for each PUCCH format. For a given PUCCHformat, two or more resource sets may also be used. The usage of one ofthe two or more resource sets may be per base station scheduling or maybe layer 3 configured (e.g., applicable to different subframe sets).

Thus, using 1 ms PUCCH for DL slot TTI (e.g., a DL transmission using areduced duration TTI may reduce the HARQ timing and retransmissiontiming. In some cases, non-low latency HARQ (e.g., legacy HARQ) may beused for UEs 115 in unfavorable channel conditions, whereas low latencyHARQ may be used in more favorable conditions. However, when a ULcontrol information is transmitting using a 1 ms TTI, a relativelylarger timing advance may be used by the UE 115-a (e.g., due torelatively longer propagation delay), which may make it difficult tomeet HARQ timeline if HARQ timing is shortened. That is, a HARQ timingfor low latency communications may be selected to accommodate parallelor concurrent legacy HARQ operations within system 200.

Thus, the base station 105-a may support more than one HARQ timingoption, and the UE 115-a may have the capability to support one or moreof these timing options. For example, UE 115-a may support a HARQ timingmode that allows for low latency DL transmissions if, for instance, theUE 115-a has advanced processing power relative to other UEs 115.Another UE 115 may support a different timing mode if it is constrainedin processing power (e.g., a machine type communication MTC device). Insome cases, base station 105-a may indicate a HARQ timing option for UE115-a, and UE 115-a may request a desired HARQ timing.

The usage of 1 ms-duration PUCCH (instead of low latency PUCCH) for HARQfeedback for DL transmission that uses a slot-duration TTI may also betied with how the slot-duration TTI is scheduled. For example, if DLtransmission in a slot-duration TTI is scheduled by a multi-TTI grant, a1 ms-duration PUCCH may be used to provide HARQ feedback. Otherwise, aPUCCH with slot-duration TTI may be used. Although, in some cases,system 200 may operate more efficiently if 1 ms-duration PUCCH is usedin many or most scenarios.

In some examples, a downlink assignment index (DAI) may also be used toindicate how many slot-duration TTI transmissions are scheduled forfeedback in a PUCCH (e.g., slot 0 only, slot 1 only, or both slotswithin a carrier and across carriers). The DAI may count, cumulativelyor in total, the number of scheduled DL transmissions. Additionally oralternatively, HARQ feedback may be sent using 1 ms-duration PUSCH witha similar timing as described herein for feedback provided in a 1ms-duration PUCCH.

In some cases, low latency HARQ timing may include UL scheduling or HARQtiming for joint grants. If a joint grant operation is supported, the ULscheduling/HARQ timing may be based on timing of slot 0. For example, acontrol channel may be legacy PDCCH or shortened EPDCCH (i.e., EPDCCHonly slot 0), where scheduling may be in both slot 0 and slot 1. Inother words, if a 1 ms-duration PUCCH is used for HARQ feedback, thecontrol channel scheduling a PUSCH transmission in slot-duration TTI maybe present in slot 0. In such cases, for slot 1 low latency PUSCHtransmission, there may be 1 ms for base station to process anddetermine whether to perform re-transmissions or not (some relaxation ispossible as in the DL, but not necessary).

In some examples, in an UL subframe, the scheduling determinations for alow latency PUSCH and 1 ms TTI PUSCH may be made in different subframes.For instance, for 1 ms-duration TTI, the scheduling determination may bemade at 4 ms or earlier; and for slot-duration TTI, the schedulingdecision may be made at 2 ms or earlier. Such scheduling may be may be asystem operator or at base station 105-a to avoid resourcefragmentation. Additionally or alternatively, a 2 ms scheduling may alsobe used for 1 ms-duration PUSCH.

In some cases, a HARQ timing mode or anticipated HARQ timing may beselected to accommodate dynamic and semi-persistent scheduling (SPS)traffic. If dynamic scheduling and SPS scheduling (of the same TTI)occurs in the same subframe, dynamic scheduling may take precedence. Ifdifferent TTIs are supported, a dynamic scheduling of a first TTI maycollide with a SPS scheduling of a second TTI in the same subframe. Forexample, there may be a 1 ms dynamic scheduling and a 1-slot SPS. Insuch cases, the slot-duration TTI SPS may be dropped (e.g., forreceiving or transmitting), while the 1 ms may take precedence. In someexamples, there may be a 1-slot dynamic scheduling and a 1 ms SPS for aDL transmission. In such cases, if the slot-duration TTI dynamic controlchannel (e.g., scheduling slot 0 data transmissions or for both slot 0and slot 1 data transmissions) is received in slot 0, 1 ms based SPS maybe dropped.

In some examples, if the slot-duration TTI dynamic control channel isreceived in slot 1, the UE may buffer potential SPS traffic for theentire subframe to determine whether it will monitor the SPS or not(e.g., the base station may still transmit SPS in slot 0, but the UE maynot be required to decode it). Alternatively, 1 ms SPS may be given ahigher priority than slot-duration TTI control channel in slot 1. Thatis, if a subframe has a 1 ms SPS for an UL transmission, the controlchannel scheduling slot 1 data transmission may not be transmitted inslot 1. In another example, there may be a 1-slot dynamic and a 1 ms SPSfor an UL transmission or during an UL TTI. In such cases, the 1 ms SPSmay be dropped. Generally, the SPS of a second TTI may be dropped due toa dynamic schedule of a first TTI in the same subframe.

Additional examples of operations and configurations of uplink anddownlink channels for low latency HARQ feedback timing are describedbelow. FIG. 3 illustrates an example of a channel configuration 300 forHARQ timing for reduced TTIs. In some cases, channel configuration 300may represent aspects of techniques performed by a UE 115 or basestation 105 as described with reference to FIGS. 1-2. Channelconfiguration 300 may represent an example based on 2-slot and 3-slotHARQ response timing as described with reference to FIGS. 1 and 2.

Low latency DL transmissions 302 may be transmitted on DL carrier 310.For example, low latency DL transmissions 302 may be transmitted duringslot 0 305-a and slot 1 305-b of DL carrier 310 during subframe 325. ULcontrol transmission 315 (i.e., a 1 ms TTI PUCCH transmissioncorresponding to the low latency DL transmissions 302) may betransmitted on UL carrier 320 in subframe 327. Low latency DLretransmissions 304 may then be transmitted on DL carrier 310 in slot 0306-a and slot 1 306-b of subframe 328, which may be four subframesafter subframe 325 (i.e., a 4 ms retransmission RTT).

Non-low latency DL transmission 329 may be transmitted on DL carrier 310in two consecutive slots (e.g., slots 0 305-a and 1 305-b) duringsubframe 325. Non-low latency UL control transmission 330 may betransmitted on UL carrier 320 in subframe 331 and the non-low latency DLretransmission 333 may be sent in subframe 335, which may be eightsubframes after subframe 325 (i.e., an 8 ms retransmission RTT).

FIG. 4 illustrates an example of a carrier configuration 400 for HARQtiming for reduced TTIs. In some cases, carrier configuration 400 mayrepresent aspects of techniques performed by a UE 115 or base station105 as described with reference to FIGS. 1-2. Configuration 400 mayrepresent an example based on 3-slot and 4-slot HARQ response timing asdescribed with reference to FIGS. 1 and 2.

Low latency DL transmissions 402 may be transmitted on DL carrier 410.For example, low latency DL transmission 402 may be transmitted duringslot 0 405-b of DL carrier 410 during subframe 425 and slot 1 405-a of apreceding subframe 427. Low latency UL control transmission 415 (i.e.,PUCCH transmission corresponding to the low latency DL transmissions402) may be transmitted on UL carrier 420 in subframe 428. Low latencyDL retransmissions 404 b may then be transmitted on DL carrier 410during slot 0 406-a and slot 1 406-b of subframe 429, which may be fivesubframes after subframe 425 (i.e., a 5 ms RTT).

Non-low latency DL transmission 430 may be transmitted on DL carrier 410in two consecutive slots of subframe 425. Non-low latency UL controltransmission 431 may be transmitted on UL carrier 420 in subframe 433and the non-low latency DL retransmission 434 may be sent in subframe435, which may be eight subframes after subframe 425 (i.e., an 8 msRRT).

FIG. 5 illustrates an example of a carrier configuration 500 for HARQtiming for reduced TTIs. In some cases, carrier configuration 500 mayrepresent aspects of techniques performed by a UE 115 or base station105 as described with reference to FIGS. 1-2. Configuration 500 mayrepresent an example based on 3-slot and 4-slot HARQ response timing asdescribed with reference to FIGS. 1 and 2.

Low latency DL transmissions 502 may be transmitted on DL carrier 510.For example, low latency DL transmission 502 may be transmitted duringslot 0 505-a and slot 1 505-b of DL carrier 510 during 525. Low latencyUL control transmission 515-a (i.e., PUCCH transmission corresponding tothe low latency DL transmission 502 during slot 505-a) and low latencyUL control transmission 515-b (i.e., PUCCH transmission corresponding tolow latency DL transmission 502 during slot 1 505-b) may be transmittedon UL carrier 520 in time periods 517 and 518, each with duration of asubframe beginning three slots after slot 0 505-a and slot 505-b,respectively. Low latency DL retransmissions 504 may then be transmittedon DL carrier 510 during slot 0 506-a and slot 1 506-b of subframe 527,which may be four subframes after subframe 525 (i.e., a 4 ms RTT).

Non-low latency DL transmission 530 may be transmitted on DL carrier 510in two consecutive slots during 525. Non-low latency UL controltransmission 531 may be transmitting on UL carrier 520 in subframe 532and the non-low latency DL retransmission 533 may be sent in subframe535, which may be eight subframes after subframe 525 (i.e., an 8 msRRT).

FIG. 6 illustrates an example of slot configurations 600 for HARQ timingfor reduced TTIs. Slot configurations 600 may represent aspects oftransmissions performed by a UE 115 as described with reference to FIG.5, and more specifically to examples of feedback transmitted during timeperiods 517 and 518 of FIG. 5.

In configuration 600-a two separate PUCCH transmissions 610 and 615 withcontrol information (e.g., ACK/NACK for separate different low latencyDL) transmissions may occupy a common slot of time periods 517-a and518-a. In some examples, the two PUCCH transmissions 610 and 615 may bemapped to the same RB, which may improve operating constraints (e.g.,such mapping may serve to limit maximum power reduction (MPR)requirements for modulation).

In configuration 600-b, a modified PUCCH 625 may be used to carry HARQresponses for multiple low latency DL transmissions. For example, 2-bitHARQ feedback may be used for each slot-duration DL transmission forwhich feedback is being sent. By way of example, the three slots of timeperiods 517-a and 518-a may provide 2-bit, 4-bit, and 2-bit HARQfeedback, respectively. For example, PUCCH format 3 may be used, whichmay have 2-bit, 4-bit, and 2-bit payload respectively for the threeslots. Alternatively, PUCCH format 1b with a modified format operationmay be used and the second slot may carry 4-bits. For instance, theremay be four data symbols in one slot, which may carry the same QPSKsymbol (2-bit). The data symbols may include two pairs of symbols thateach carry a separate QPSK symbol, thus making a 4-bit payload in oneslot. So, for spreading length four, for UEs 115 capable of such reducedduration HARQ timing may use spreading codes [+1, +1, +1, +1] or [+1,+1, −1, −1], and legacy PUCCH may still be multiplexed in the sameresource block (RB) if UEs 115 transmitting legacy PUCCH use spreadingcodes [+1, −1, +1, −1] or [+1, −1, −1, +1], for example.

Additionally or alternatively, configuration 600-b may support otheraspects of HARQ timing for reduced TTIs. For example, if a UE 115 isconfigured to use a modified uplink format and does not detect a grantfor the second slot of a DL transmission (e.g., miss-detection), thebase station may not know whether the grant was received or not. So insome cases, configuration 600-b may allow the second pair (i.e. last twosingle carrier frequency division multiplexing (SC-FDM) symbols) of thesecond slot (i.e., the overlapping slot of time periods 517-a and 518-a)empty. Orthogonality may still be maintained in such cases.

Alternatively, the second slot of configuration 600-b may be arranged sothat the first two symbols may carry the first two bits, b₀ and b₁, thesecond two symbols may carry b₂ and b₃ bits, but an XOR operation of thefirst and second bits respectively, i.e. b₀ XOR b₂ and b₁ XOR b₃ may beused to indicate whether a grant in the second slot was received. Forexample, when the base station does not schedule the second slot, thebase station may determine that b₂=NAK and b₃=NAK, so b₀ and b₁ may berepeated. Performance loss may be minimal in this example, as comparedwith alternative ways of conveying similar information. When the basestation schedules the second slot, bits may be decoded jointly and theremay be some performance loss due to error propagation (i.e. error in onebit creates errors in two bits).

Configuration 600-b may also depend, for example, on an orthogonal covercode (OCC) employed. For instance, if the OCC is length three discreteFourier transform (DFT), (e.g., OCC [1, 1, 1] for legacy PUCCH; otherOCC codes may be [1, e^(j) ² ^(π/3)), e^((j) ⁴ ^(π/3))] or [1, e^(j) ⁴^(π/3)), e^(j) ² ^(π/3))]). Among the 3 symbols in a slot for PUCCH (s₀,s₁, s₂), s₀ may carry ACK/NAK for the first DL slot-TTI transmission, s₂may carry ACK/NAK for the second DL slot-TTI transmission, and s₂ may bea “parity,” such that s₂=−(s₀+s₁). In such cases, orthogonality withlegacy operations may be maintained since s₀+s₁+s₂=0. If the threereceived symbols are r₀, r₁, and r₂, then the original symbols may berecovered as s₀=−(2r₀−r₁−r₂)/3, and s₁=(2r₁−r₀−r₂)/3. Accordingly, theHARQ timing described with reference to FIGS. 5 and 6 may provide forvarious options to efficiently transmit HARQ feedback for low latencytransmissions while maintaining compatibility with legacy operation.

FIG. 7 illustrates an example of a carrier configuration 700 for HARQtiming for reduced TTIs. In some cases, carrier configuration 700 mayrepresent aspects of techniques performed by a UE 115 or base station105 as described with reference to FIGS. 1-2. Configuration 700 mayrepresent an example based on 6-slot HARQ response timing as describedwith reference to FIGS. 1-2.

Low latency DL transmissions 702 transmissions may be transmitted on DLcarrier 710. For example, low latency DL transmission 702 may bescheduled during slot 0 705-a and slot 1 705-b of DL carrier 710 duringsubframe 725. Low latency UL control transmission 715 (i.e., PUCCHtransmission corresponding to the low latency DL transmissions 702) maybe transmitted on UL carrier 720 in subframe 730. Low latency DLretransmissions 704 may then be transmitted on DL carrier 710 duringslot 0 706-a and slot 1 706-b of subframe 731, which may be sixsubframes after subframe 725 (i.e., a 6 ms RTT).

Non-low latency DL transmission 732 may be transmitted on DL carrier 710in two consecutive slots during subframe 725). Non-low latency ULcontrol transmission 733 may be transmitted on UL carrier 720 also insubframe 730, and the non-low latency DL retransmission 734 may be sentin subframe 735, which may be eight subframes after subframe 725 (i.e.,an 8 ms RTT).

FIG. 8 illustrates an example of a process flow 800 for HARQ timing forreduced TTIs in accordance with various aspects of the presentdisclosure. Process flow 800 may include base station 105-a and UE115-a, which may be examples of the corresponding devices described withreference to FIG. 1-2.

At step 805, base station 105-a may receive an indication of UE 115-aHARQ feedback capability. At step 810, base station 105-a may identify acapability of UE 115-a to provide HARQ feedback associated with TTIs ofa second duration. At step 815, base station 105-a may select a HARQtiming mode based at least in part on the capability of the UE 115-a. Atstep 820, base station 105-a may transmit an indication of the HARQtiming mode to the UE 115-a.

At step 825, base station 105-a may transmit a first transport block(TB) during a first transmission time interval (TTI) and second TBduring a second TTI of a second duration. Additionally, the first TB maybe associated with an uplink (UL) resource for HARQ feedback, which maybe based at least in part on a downlink (DL) control channel transmittedduring a time period four times the second duration prior to thetransmission of the first TB.

At step 830, base station 105-a may identify a feedback time periodbased at least in part on the HARQ timing mode. Additionally, the HARQtiming mode may include a first HARQ response time of four times thesecond duration and a second HARQ response time of three times thesecond duration.

At step 835, base station 105-a may receive one or more HARQ feedbackmessages associated with the first and second TB, wherein the one ormore HARQ feedback messages are received during a TTI of the firstduration. Additionally, the one or more HARQ feedback messages maycomprise a first HARQ feedback message and a second HARQ feedbackmessage, where the first HARQ feedback message is associated with thefirst TB and the second HARQ feedback message is associated with thesecond TB. Additionally, the first and second HARQ feedback messages maybe configured according to the first duration.

At step 840, base station 105-a may retransmit the first TB or thesecond TB based at least in part on a retransmission time of ten timesthe second duration.

FIG. 9 shows a block diagram of a wireless device 900 that supports HARQtiming for reduced TTIs in accordance with various aspects of thepresent disclosure. Wireless device 900 may be an example of aspects ofa UE 115 or base station 105 described with reference to FIGS. 1 and 2.Wireless device 900 may include receiver 905, HARQ timing manager 910and transmitter 915. Wireless device 900 may also include a processor.Each of these components may be in communication with each other.

The receiver 905 may receive information such as packets, user data, orcontrol information associated with various information channels (e.g.,control channels, data channels, and information related to HARQ timingfor reduced TTIs, etc.). Information may be passed on to othercomponents of the device. The receiver 905 may be an example of aspectsof the transceiver 1225 described with reference to FIG. 12.

The HARQ timing manager 910 may determine a HARQ timing mode based onone or more capabilities of a UE to provide HARQ feedback in response tocommunications using TTIs of the second duration, and communicate, incombination with receiver 905 or transmitter 915, or both, using theHARQ timing mode. The HARQ timing manager 910 may also be an example ofaspects of the HARQ timing manager 1205 described with reference to FIG.12.

The transmitter 915 may transmit signals received from other componentsof wireless device 900. In some examples, the transmitter 915 may becollocated with a receiver in a transceiver module. For example, thetransmitter 915 may be an example of aspects of the transceiver 1225described with reference to FIG. 12. The transmitter 915 may include asingle antenna, or it may include a plurality of antennas.

FIG. 10 shows a block diagram of a wireless device 1000 that supportsHARQ timing for reduced TTIs in accordance with various aspects of thepresent disclosure. Wireless device 1000 may be an example of aspects ofa wireless device 900 or a UE 115 or base station 105 described withreference to FIGS. 1, 2 and 9. Wireless device 1000 may include receiver1005, HARQ timing manager 1010 and transmitter 1025. Wireless device1000 may also include a processor. Each of these components may be incommunication with one another.

The receiver 1005 may receive information which may be passed on toother components of the device. The receiver 1005 may also perform thefunctions described with reference to the receiver 905 of FIG. 9. Thereceiver 1005 may be an example of aspects of the transceiver 1225described with reference to FIG. 12.

The HARQ timing manager 1010 may be an example of aspects of HARQ timingmanager 910 described with reference to FIG. 9. The HARQ timing manager1010 may include HARQ timing mode component 1015 and low latencycommunication component 1020. The HARQ timing manager 1010 may be anexample of aspects of the HARQ timing manager 1205 described withreference to FIG. 12.

The HARQ timing mode component 1015 may transmit an indication of theone or more capabilities of a UE to a base station, receive anindication of a set of HARQ timing modes from a base station, anddetermine a HARQ timing mode based on one or more capabilities of a UEto provide HARQ feedback in response to communications using TTIs of thesecond duration. The operations of HARQ timing mode component 1015 maybe performed in combination with receiver 1005 or transmitter 1025 invarious examples.

The low latency communication component 1020 may communicate, incombination with receiver 1005 or transmitter 1025, using the HARQtiming mode. In some cases, the communicating includes receiving a firstTB during a first TTI and a second TB during a second TTI, where thefirst TTI and the second TTI each have the second duration. In somecases, the first TTI is within a latter part of a first time periodhaving the first duration and the second TTI is within an initial partof a second time period having the first duration. In some cases, thecommunicating includes transmitting a first TB during a first TTI and asecond TB during a second TTI, where the first TTI and the second TTIeach have the second duration.

The transmitter 1025 may transmit signals received from other componentsof wireless device 1000. In some examples, the transmitter 1025 may becollocated with a receiver in a transceiver module. For example, thetransmitter 1025 may be an example of aspects of the transceiver 1225described with reference to FIG. 12. The transmitter 1025 may utilize asingle antenna, or it may utilize a plurality of antennas.

FIG. 11 shows a block diagram of a HARQ timing manager 1100 which may bean example of the corresponding component of wireless device 900 orwireless device 1000. That is, HARQ timing manager 1100 may be anexample of aspects of HARQ timing manager 910 or HARQ timing manager1010 described with reference to FIGS. 9 and 10. The HARQ timing manager1100 may also be an example of aspects of the HARQ timing manager 1205described with reference to FIG. 12.

The HARQ timing manager 1100 may include feedback time period component1105, HARQ feedback component 1110, HARQ timing mode component 1115,HARQ timing mode request component 1120, UL control configurationcomponent 1125, PUCCH resource offset component 1130, DL transmissionindicator component 1135, and low latency communication component 1140.Each of these modules may communicate, directly or indirectly, with oneanother (e.g., via one or more buses).

The feedback time period component 1105 may identify a feedback timeperiod based on the HARQ timing mode, where the HARQ timing modeincludes a first HARQ response time and a second HARQ response time thatis equal to the first HARQ response time, or where the HARQ timing modeincludes a first HARQ response time and a second HARQ response time thatis less than the first HARQ response time.

The HARQ feedback component 1110 may transmit or receive one or moreHARQ feedback messages associated with the first or the second TB duringthe feedback time period, where the one or more HARQ feedback messagesare received during a TTI of the first duration. The HARQ feedbackcomponent 1110 may perform operations in combination with a receiver1005 or transmitter 1025 of FIG. 10. In some cases, the one or more HARQfeedback messages include a first HARQ feedback message and a secondHARQ feedback message distinct from the first HARQ feedback message. Insome cases, a latter portion of the first HARQ feedback message and aninitial portion of the second HARQ feedback message are multiplexedusing at least one of a PUCCH format capable of carrying more than twobits, a division of bits between the latter portion of the first HARQfeedback message and the initial portion of the second HARQ feedbackmessage, joint coding of one or more bits of the first HARQ feedbackmessage and the second HARQ feedback message, a combination of bitsbased on an orthogonal cover code (OCC) and at least one parity bit, orany combination thereof.

The HARQ timing mode component 1115 may transmit an indication of theone or more capabilities of a UE to a base station, receive anindication of a set of HARQ timing modes from a base station, anddetermine a HARQ timing mode based on one or more capabilities of a UEto provide HARQ feedback in response to communications using TTIs of thesecond duration. The operations of HARQ timing mode component 1115 maybe performed in combination with receiver 1005 or transmitter 1025 ofFIG. 10.

The HARQ timing mode request component 1120 may, in combination withtransmitter 1025, transmit a HARQ timing mode request in response to theindication, where the HARQ timing mode is selected from the set of HARQtiming modes based on the HARQ timing mode request. The UL controlconfiguration component 1125 may identify an UL control configurationbased on the HARQ timing mode, and transmit an indication of the ULcontrol configuration to a UE.

The PUCCH resource offset component 1130 may identify a first PUCCHresource offset for UL transmissions that use TTIs of the first durationand a second PUCCH resource offset for UL transmissions that use TTIs ofthe second duration. In some cases, the second PUCCH resource offset isidentified based on the first PUCCH resource offset and a delta value.In some cases, the first PUCCH resource offset or the second PUCCHresource offset is identified based on a PUCCH format. In some cases,the one or more resource sets for UL transmissions are associated witheach PUCCH format of a set of PUCCH formats, and where the one or moreresource sets are each associated with a different base station or layerthree configuration.

The DL transmission indicator component 1135 may identify a firstscheduled DL transmission indicator associated with TTIs of the firstduration and a second scheduled DL transmission indicator associatedwith TTIs of the second duration.

The low latency communication component 1140 may communicate using theHARQ timing mode. In some cases, the communicating includes transmittingor receiving a first TB during a first TTI and a second TB during asecond TTI, where the first TTI and the second TTI each have the secondduration. The operations of low latency communication component 1140 maybe performed in combination with receiver 1005 or transmitter 1025 ofFIG. 10.

FIG. 12 shows a diagram of a system 1200 including a device thatsupports HARQ timing for reduced TTIs in accordance with various aspectsof the present disclosure. For example, system 1200 may include UE115-c, which may be an example of a wireless device 900, a wirelessdevice 1000, or a UE 115 as described with reference to FIGS. 1, 2, and9 through 11.

UE 115-c may also include HARQ timing manager 1205, memory 1210,processor 1220, transceiver 1225, antenna 1230, and ECC module 1235.Each of these modules may communicate, directly or indirectly, with oneanother (e.g., via one or more buses). The HARQ timing manager 1205 maybe an example of a primary module as described with reference to FIGS. 9through 11.

The memory 1210 may include random access memory (RAM) and read onlymemory (ROM). The memory 1210 may store computer-readable,computer-executable software including instructions that, when executed,cause the processor to perform various functions described herein (e.g.,HARQ timing for reduced TTIs, etc.). In some cases, the software 1215may not be directly executable by the processor but may cause a computer(e.g., when compiled and executed) to perform functions describedherein. The processor 1220 may include an intelligent hardware device,(e.g., a central processing unit (CPU), a microcontroller, anapplication specific integrated circuit (ASIC), etc.)

The transceiver 1225 may communicate bi-directionally, via one or moreantennas, wired, or wireless links, with one or more networks, asdescribed above. For example, the transceiver 1225 may communicatebi-directionally with a base station 105 or a UE 115. The transceiver1225 may also include a modem to modulate the packets and provide themodulated packets to the antennas for transmission, and to demodulatepackets received from the antennas. In some cases, the wireless devicemay include a single antenna 1230. However, in some cases the device mayhave more than one antenna 1230, which may be capable of concurrentlytransmitting or receiving multiple wireless transmissions.

ECC module 1235 may enable operations using enhanced component carriers(ECCs) such as communication using shared or unlicensed spectrum, usingreduced TTIs or subframe durations, or using a large number of componentcarriers.

FIG. 13 shows a diagram of a wireless system 1300 including a deviceconfigured that supports HARQ timing for reduced TTIs in accordance withvarious aspects of the present disclosure. For example, system 1300 mayinclude base station 105-d, which may be an example of a wireless device900, a wireless device 1000, or a base station 105 as described withreference to FIGS. 1, 2 and 9 through 11. Base station 105-d may alsoinclude components for bi-directional voice and data communicationsincluding components for transmitting communications and components forreceiving communications. For example, base station 105-d maycommunicate bi-directionally with one or more UEs 115.

Base station 105-d may also include primary module 1305, memory 1310,processor 1320, transceiver 1325, antenna 1330, base stationcommunications module 1335 and network communications module 1340. Eachof these modules may communicate, directly or indirectly, with oneanother (e.g., via one or more buses). The primary module 1305 may be anexample of a primary module as described with reference to FIGS. 9through 11.

The memory 1310 may include RAM and ROM. The memory 1310 may storecomputer-readable, computer-executable software including instructionsthat, when executed, cause the processor to perform various functionsdescribed herein (e.g., HARQ timing for reduced TTIs, etc.). In somecases, the software 1315 may not be directly executable by the processorbut may cause a computer (e.g., when compiled and executed) to performfunctions described herein. The processor 1320 may include anintelligent hardware device, (e.g., a CPU, a microcontroller, an ASIC,etc.)

The transceiver 1325 may communicate bi-directionally, via one or moreantennas, wired, or wireless links, with one or more networks, asdescribed above. For example, the transceiver 1325 may communicatebi-directionally with a base station 105 or a UE 115. The transceiver1325 may also include a modem to modulate the packets and provide themodulated packets to the antennas for transmission, and to demodulatepackets received from the antennas. In some cases, the wireless devicemay include a single antenna 1330. However, in some cases the device mayhave more than one antenna 1230, which may be capable of concurrentlytransmitting or receiving multiple wireless transmissions.

The base station communications module 1335 may manage communicationswith other base station 105, and may include a controller or schedulerfor controlling communications with UEs 115 in cooperation with otherbase stations 105. For example, the base station communications module1335 may coordinate scheduling for transmissions to UEs 115 for variousinterference mitigation techniques such as beamforming or jointtransmission. In some examples, base station communications module 1335may provide an X2 interface within an LTE/LTE-A wireless communicationnetwork technology to provide communication between base stations 105.

The network communications module 1340 may manage communications withthe core network (e.g., via one or more wired backhaul links). Forexample, the network communications module 1340 may manage the transferof data communications for client devices, such as one or more UEs 115.

FIG. 14 shows a flowchart illustrating a method 1400 for HARQ timing forreduced TTIs in accordance with various aspects of the presentdisclosure. The operations of method 1400 may be implemented by a devicesuch as a UE 115 or base station 105 or its components as described withreference to FIGS. 1 and 2. For example, the operations of method 1400may be performed by the HARQ timing manager as described herein. In someexamples, the UE 115 or base station 105 may execute a set of codes tocontrol the functional elements of the device to perform the functionsdescribed below. Additionally or alternatively, the UE 115 or basestation 105 may perform aspects of functions described below usingspecial-purpose hardware.

At block 1405, the UE 115 or base station 105 operating in a system thatsupports communications using TTIs of a first duration and a secondduration may determine a HARQ timing mode based on one or morecapabilities of a UE to provide HARQ feedback in response tocommunications using TTIs of the second duration as described above withreference to FIGS. 2 through 8. In certain examples, the operations ofblock 1405 may be performed by the HARQ timing mode component asdescribed with reference to FIGS. 10 and 11.

At block 1410, the UE 115 or base station 105 may communicate using theHARQ timing mode as described above with reference to FIGS. 2 through 8.In certain examples, the operations of block 1410 may be performed bythe low latency communication component as described with reference toFIGS. 10 and 11 or the transceivers 1225 or 1325 as described withreference to FIGS. 12 and 13.

FIG. 15 shows a flowchart illustrating a method 1500 for HARQ timing forreduced TTIs in accordance with various aspects of the presentdisclosure. The operations of method 1500 may be implemented by a devicesuch as a UE 115 or its components as described with reference to FIGS.1 and 2. For example, the operations of method 1500 may be performed bythe HARQ timing manager as described herein. In some examples, the UE115 may execute a set of codes to control the functional elements of thedevice to perform the functions described below. Additionally oralternatively, the UE 115 may perform aspects of the functions describedbelow using special-purpose hardware.

At block 1505, the UE 115 operating in a system that supportscommunications using TTIs of a first duration and a second duration maydetermine a HARQ timing mode based on one or more capabilities of a UEto provide HARQ feedback in response to communications using TTIs of thesecond duration as described above with reference to FIGS. 2 through 8.In certain examples, the operations of block 1505 may be performed bythe HARQ timing mode component as described with reference to FIGS. 10and 11.

At block 1510, the UE 115 may communicate using the HARQ timing mode asdescribed above with reference to FIGS. 2 through 8. In some cases, thecommunicating includes receiving a first TB during a first TTI and asecond TB during a second TTI, where the first TTI and the second TTIeach have the second duration. In certain examples, the operations ofblock 1510 may be performed by the low latency communication componentas described with reference to FIGS. 10 and 11 or the transceiver 1225as described with reference to FIG. 12.

At block 1515, the UE 115 may identify a feedback time period based onthe HARQ timing mode, where the HARQ timing mode includes a first HARQresponse time and a second HARQ response time that is less than thefirst HARQ response time as described above with reference to FIGS. 2through 8. In certain examples, the operations of block 1515 may beperformed by the feedback time period component as described withreference to FIGS. 10 and 11.

At block 1520, the UE 115 may transmit one or more HARQ feedbackmessages associated with the first or the second TB during the feedbacktime period, where the one or more HARQ feedback messages are receivedduring a TTI of the first duration as described above with reference toFIGS. 2 through 8. In certain examples, the operations of block 1520 maybe performed by the HARQ feedback component as described with referenceto FIGS. 10 and 11 or the transceiver 1225 as described with referenceto FIG. 12.

FIG. 16 shows a flowchart illustrating a method 1600 for HARQ timing forreduced TTIs in accordance with various aspects of the presentdisclosure. The operations of method 1600 may be implemented by a devicesuch as a UE 115 or its components as described with reference to FIGS.1 and 2. For example, the operations of method 1600 may be performed bythe HARQ timing manager as described herein. In some examples, the UE115 may execute a set of codes to control the functional elements of thedevice to perform the functions described below. Additionally oralternatively, the UE 115 may perform aspects the functions describedbelow using special-purpose hardware.

At block 1605, the UE 115 operating in a system that supportscommunications using TTIs of a first duration and a second duration maydetermine a HARQ timing mode based on one or more capabilities of a UEto provide HARQ feedback in response to communications using TTIs of thesecond duration as described above with reference to FIGS. 2 through 8.In certain examples, the operations of block 1605 may be performed bythe HARQ timing mode component as described with reference to FIGS. 10and 11.

At block 1610, the UE 115 may communicate using the HARQ timing mode asdescribed above with reference to FIGS. 2 through 8. In some cases, thecommunicating includes receiving a first TB during a first TTI and asecond TB during a second TTI, where the first TTI and the second TTIeach have the second duration. In certain examples, the operations ofblock 1610 may be performed by the low latency communication componentas described with reference to FIGS. 10 and 11 or the transceivers 1225as described with reference to FIG. 12.

At block 1615, the UE 115 may identify a feedback time period based onthe HARQ timing mode, where the HARQ timing mode includes a first HARQresponse time and a second HARQ response time that is equal to the firstHARQ response time as described above with reference to FIGS. 2 through8. In certain examples, the operations of block 1615 may be performed bythe feedback time period component as described with reference to FIGS.10 and 11.

At block 1620, the UE 115 may transmit one or more HARQ feedbackmessages associated with the first or the second TB during the feedbacktime period, where the one or more HARQ feedback messages are receivedduring a TTI of the first duration as described above with reference toFIGS. 2 through 8. In certain examples, the operations of block 1620 maybe performed by the HARQ feedback component as described with referenceto FIGS. 10 and 11 or the transceiver 1225 as described with referenceto FIG. 12.

FIG. 17 shows a flowchart illustrating a method 1700 for HARQ timing forreduced TTIs in accordance with various aspects of the presentdisclosure. The operations of method 1700 may be implemented by a devicesuch as a UE 115 or its components as described with reference to FIGS.1 and 2. For example, the operations of method 1700 may be performed bythe HARQ timing manager as described herein. In some examples, the UE115 may execute a set of codes to control the functional elements of thedevice to perform the functions described below. Additionally oralternatively, the UE 115 may perform aspects the functions describedbelow using special-purpose hardware.

At block 1705, the UE 115 operating in a system that supportscommunications using TTIs of a first duration and a second duration maytransmit an indication of the one or more capabilities of a UE to a basestation as described above with reference to FIGS. 2 through 8. Incertain examples, the operations of block 1705 may be performed by theHARQ timing mode component as described with reference to FIGS. 10 and11.

At block 1710, the UE 115 may determine a HARQ timing mode based on oneor more capabilities of a UE to provide HARQ feedback in response tocommunications using TTIs of the second duration as described above withreference to FIGS. 2 through 8. In certain examples, the operations ofblock 1710 may be performed by the HARQ timing mode component asdescribed with reference to FIGS. 10 and 11.

At block 1715, the UE 115 may communicate using the HARQ timing mode asdescribed above with reference to FIGS. 2 through 8. In certainexamples, the operations of block 1715 may be performed by the lowlatency communication component as described with reference to FIGS. 10and 11 or the transceiver 1225 as described with reference to FIG. 12.

FIG. 18 shows a flowchart illustrating a method 1800 for HARQ timing forreduced TTIs in accordance with various aspects of the presentdisclosure. The operations of method 1800 may be implemented by a devicesuch as a base station 105 or its components as described with referenceto FIGS. 1 and 2. For example, the operations of method 1800 may beperformed by the HARQ timing manager as described herein. In someexamples, the base station 105 may execute a set of codes to control thefunctional elements of the device to perform the functions describedbelow. Additionally or alternatively, the base station 105 may performaspects the functions described below using special-purpose hardware.

At block 1805, the base station 105 operating in a system that supportscommunications using TTIs of a first duration and a second duration maydetermine a HARQ timing mode based on one or more capabilities of a UEto provide HARQ feedback in response to communications using TTIs of thesecond duration as described above with reference to FIGS. 2 through 8.In certain examples, the operations of block 1805 may be performed bythe HARQ timing mode component as described with reference to FIGS. 10and 11.

At block 1810, the base station 105 may communicate using the HARQtiming mode as described above with reference to FIGS. 2 through 8. Insome cases, the communicating includes transmitting a first TB during afirst TTI and a second TB during a second TTI, where the first TTI andthe second TTI each have the second duration. In certain examples, theoperations of block 1810 may be performed by the low latencycommunication component as described with reference to FIGS. 10 and 11or the transceiver 1325 as described with reference to FIG. 13.

At block 1815, the base station 105 may identify a feedback time periodbased on the HARQ timing mode, where the HARQ timing mode includes afirst HARQ response time and a second HARQ response time that is lessthan the first HARQ response time as described above with reference toFIGS. 2 through 8. In certain examples, the operations of block 1815 maybe performed by the feedback time period component as described withreference to FIGS. 10 and 11.

At block 1820, the base station 105 may receive one or more HARQfeedback messages associated with the first or the second TB during thefeedback time period, where the one or more HARQ feedback messages arereceived during a TTI of the first duration as described above withreference to FIGS. 2 through 8. In certain examples, the operations ofblock 1820 may be performed by the HARQ feedback component as describedwith reference to FIGS. 10 and 11 or the transceiver 1325 as describedwith reference to FIG. 13.

FIG. 19 shows a flowchart illustrating a method 1900 for HARQ timing forreduced TTIs in accordance with various aspects of the presentdisclosure. The operations of method 1900 may be implemented by a devicesuch as a base station 105 or its components as described with referenceto FIGS. 1 and 2. For example, the operations of method 1900 may beperformed by the HARQ timing manager as described herein. In someexamples, the base station 105 may execute a set of codes to control thefunctional elements of the device to perform the functions describedbelow. Additionally or alternatively, the base station 105 may performaspects the functions described below using special-purpose hardware.

At block 1905, the base station 105 operating in a system that supportscommunications using TTIs of a first duration and a second duration maydetermine a HARQ timing mode based on one or more capabilities of a UEto provide HARQ feedback in response to communications using TTIs of thesecond duration as described above with reference to FIGS. 2 through 8.In certain examples, the operations of block 1905 may be performed bythe HARQ timing mode component as described with reference to FIGS. 10and 11.

At block 1910, the base station 105 may communicate using the HARQtiming mode as described above with reference to FIGS. 2 through 8. Insome cases, the communicating includes transmitting a first TB during afirst TTI and a second TB during a second TTI, where the first TTI andthe second TTI each have the second duration. In certain examples, theoperations of block 1910 may be performed by the low latencycommunication component as described with reference to FIGS. 10 and 11or the transceiver 1325 as described with reference to FIG. 13.

At block 1915, the base station 105 may identify a feedback time periodbased on the HARQ timing mode, where the HARQ timing mode includes afirst HARQ response time and a second HARQ response time that is equalto the first HARQ response time as described above with reference toFIGS. 2 through 8. In certain examples, the operations of block 1915 maybe performed by the feedback time period component as described withreference to FIGS. 10 and 11.

At block 1920, the base station 105 may receive one or more HARQfeedback messages associated with the first or the second TB during thefeedback time period, where the one or more HARQ feedback messages arereceived during a TTI of the first duration as described above withreference to FIGS. 2 through 8. In certain examples, the operations ofblock 1920 may be performed by the HARQ feedback component as describedwith reference to FIGS. 10 and 11 or the transceiver 1325 as describedwith reference to FIG. 13.

It should be noted that these methods and processes describe possibleimplementation, and that the operations and the steps may be rearrangedor otherwise modified such that other implementations are possible. Insome examples, aspects from two or more of the methods may be combined.For example, aspects of each of the methods may include steps or aspectsof the other methods, or other steps or techniques described herein.Thus, aspects of the disclosure may provide for HARQ timing for reducedTTIs.

The description herein is provided to enable a person skilled in the artto make or use the disclosure. Various modifications to the disclosurewill be readily apparent to those skilled in the art, and the genericprinciples defined herein may be applied to other variations withoutdeparting from the scope of the disclosure. Thus, the disclosure is notto be limited to the examples and designs described herein but is to beaccorded the broadest scope consistent with the principles and novelfeatures disclosed herein.

The functions described herein may be implemented in hardware, softwareexecuted by a processor, firmware, or any combination thereof. Ifimplemented in software executed by a processor, the functions may bestored on or transmitted over as one or more instructions or code on acomputer-readable medium. Other examples and implementations are withinthe scope of the disclosure and appended claims. For example, due to thenature of software, functions described above can be implemented usingsoftware executed by a processor, hardware, firmware, hardwiring, orcombinations of any of these. Features implementing functions may alsobe physically located at various positions, including being distributedsuch that portions of functions are implemented at different physicallocations. Also, as used herein, including in the claims, “or” as usedin a list of items (for example, a list of items prefaced by a phrasesuch as “at least one of” or “one or more”) indicates an inclusive listsuch that, for example, a list of at least one of A, B, or C means A orB or C or AB or AC or BC or ABC (i.e., A and B and C).

Computer-readable media includes both non-transitory computer storagemedia and communication media including any medium that facilitatestransfer of a computer program from one place to another. Anon-transitory storage medium may be any available medium that can beaccessed by a general purpose or special purpose computer. By way ofexample, and not limitation, non-transitory computer-readable media cancomprise RAM, ROM, electrically erasable programmable read only memory(EEPROM), compact disk (CD) ROM or other optical disk storage, magneticdisk storage or other magnetic storage devices, or any othernon-transitory medium that can be used to carry or store desired programcode means in the form of instructions or data structures and that canbe accessed by a general-purpose or special-purpose computer, or ageneral-purpose or special-purpose processor. Also, any connection isproperly termed a computer-readable medium. For example, if the softwareis transmitted from a website, server, or other remote source using acoaxial cable, fiber optic cable, twisted pair, digital subscriber line(DSL), or wireless technologies such as infrared, radio, and microwave,then the coaxial cable, fiber optic cable, twisted pair, DSL, orwireless technologies such as infrared, radio, and microwave areincluded in the definition of medium. Disk and disc, as used herein,include CD, laser disc, optical disc, digital versatile disc (DVD),floppy disk and Blu-ray disc where disks usually reproduce datamagnetically, while discs reproduce data optically with lasers.Combinations of the above are also included within the scope ofcomputer-readable media.

Techniques described herein may be used for various wirelesscommunications systems such as CDMA, TDMA, FDMA, OFDMA, single carrierfrequency division multiple access (SC-FDMA), and other systems. Theterms “system” and “network” are often used interchangeably. A CDMAsystem may implement a radio technology such as CDMA2000, UniversalTerrestrial Radio Access (UTRA), etc. CDMA2000 covers IS-2000, IS-95,and IS-856 standards. IS-2000 Releases 0 and A are commonly referred toas CDMA2000 1×, 1×, etc. IS-856 (TIA-856) is commonly referred to asCDMA2000 1×EV-DO, High Rate Packet Data (HRPD), etc. UTRA includesWideband CDMA (WCDMA) and other variants of CDMA. A TDMA system mayimplement a radio technology such as (Global System for Mobilecommunications (GSM)). An OFDMA system may implement a radio technologysuch as Ultra Mobile Broadband (UMB), Evolved UTRA (E-UTRA), IEEE802.11, IEEE 802.16 (WiMAX), IEEE 802.20, Flash-OFDM, etc. UTRA andE-UTRA are part of Universal Mobile Telecommunications system (UniversalMobile Telecommunications System (UMTS)). 3GPP LTE and LTE-advanced(LTE-A) are new releases of UMTS that use E-UTRA. UTRA, E-UTRA, UMTS,LTE, LTE-a, and GSM are described in documents from an organizationnamed “3rd Generation Partnership Project” (3GPP). CDMA2000 and UMB aredescribed in documents from an organization named “3rd GenerationPartnership Project 2” (3GPP2). The techniques described herein may beused for the systems and radio technologies mentioned above as well asother systems and radio technologies. The description herein, however,describes an LTE system for purposes of example, and LTE terminology isused in much of the description above, although the techniques areapplicable beyond LTE applications.

In LTE/LTE-A networks, including networks described herein, the termevolved node B (eNB) may be generally used to describe the basestations. The wireless communications system or systems described hereinmay include a heterogeneous LTE/LTE-A network in which different typesof eNBs provide coverage for various geographical regions. For example,each eNB or base station may provide communication coverage for a macrocell, a small cell, or other types of cell. The term “cell” is a 3GPPterm that can be used to describe a base station, a carrier or componentcarrier (CC) associated with a base station, or a coverage area (e.g.,sector, etc.) of a carrier or base station, depending on context.

Base stations may include or may be referred to by those skilled in theart as a base transceiver station, a radio base station, an access point(AP), a radio transceiver, a NodeB, eNodeB (eNB), Home NodeB, a HomeeNodeB, or some other suitable terminology. The geographic coverage areafor a base station may be divided into sectors making up only a portionof the coverage area. The wireless communications system or systemsdescribed herein may include base stations of different types (e.g.,macro or small cell base stations). The UEs described herein may be ableto communicate with various types of base stations and network equipmentincluding macro eNBs, small cell eNBs, relay base stations, and thelike. There may be overlapping geographic coverage areas for differenttechnologies. In some cases, different coverage areas may be associatedwith different communication technologies. In some cases, the coveragearea for one communication technology may overlap with the coverage areaassociated with another technology. Different technologies may beassociated with the same base station, or with different base stations.

A macro cell generally covers a relatively large geographic area (e.g.,several kilometers in radius) and may allow unrestricted access by UEswith service subscriptions with the network provider. A small cell is alower-powered base stations, as compared with a macro cell, that mayoperate in the same or different (e.g., licensed, unlicensed, etc.)frequency bands as macro cells. Small cells may include pico cells,femto cells, and micro cells according to various examples. A pico cell,for example, may cover a small geographic area and may allowunrestricted access by UEs with service subscriptions with the networkprovider. A femto cell may also cover a small geographic area (e.g., ahome) and may provide restricted access by UEs having an associationwith the femto cell (e.g., UEs in a closed subscriber group (CSG), UEsfor users in the home, and the like). An eNB for a macro cell may bereferred to as a macro eNB. An eNB for a small cell may be referred toas a small cell eNB, a pico eNB, a femto eNB, or a home eNB. An eNB maysupport one or multiple (e.g., two, three, four, and the like) cells(e.g., CCs). A UE may be able to communicate with various types of basestations and network equipment including macro eNBs, small cell eNBs,relay base stations, and the like.

The wireless communications system or systems described herein maysupport synchronous or asynchronous operation. For synchronousoperation, the base stations may have similar frame timing, andtransmissions from different base stations may be approximately alignedin time. For asynchronous operation, the base stations may havedifferent frame timing, and transmissions from different base stationsmay not be aligned in time. The techniques described herein may be usedfor either synchronous or asynchronous operations.

The DL transmissions described herein may also be called forward linktransmissions while the UL transmissions may also be called reverse linktransmissions. Each communication link described herein including, forexample, wireless communications system 100 and 200 of FIGS. 1 and 2 mayinclude one or more carriers, where each carrier may be a signal made upof multiple sub-carriers (e.g., waveform signals of differentfrequencies). Each modulated signal may be sent on a differentsub-carrier and may carry control information (e.g., reference signals,control channels, etc.), overhead information, user data, etc. Thecommunication links described herein (e.g., communication links 125 ofFIG. 1) may transmit bidirectional communications using frequencydivision duplex (FDD) (e.g., using paired spectrum resources) or timedivision duplex (TDD) operation (e.g., using unpaired spectrumresources). Frame structures may be defined for FDD (e.g., framestructure type 1) and TDD (e.g., frame structure type 2).

Thus, aspects of the disclosure may provide for HARQ timing for reducedTTIs. It should be noted that these methods describe possibleimplementations, and that the operations and the steps may be rearrangedor otherwise modified such that other implementations are possible. Insome examples, aspects from two or more of the methods may be combined.

The various illustrative blocks and modules described in connection withthe disclosure herein may be implemented or performed with ageneral-purpose processor, a digital signal processor (DSP), an ASIC, anfield programmable gate array (FPGA) or other programmable logic device,discrete gate or transistor logic, discrete hardware components, or anycombination thereof designed to perform the functions described herein.A general-purpose processor may be a microprocessor, but in thealternative, the processor may be any conventional processor,controller, microcontroller, or state machine. A processor may also beimplemented as a combination of computing devices (e.g., a combinationof a DSP and a microprocessor, multiple microprocessors, one or moremicroprocessors in conjunction with a DSP core, or any other suchconfiguration). Thus, the functions described herein may be performed byone or more other processing units (or cores), on at least oneintegrated circuit (IC). In various examples, different types of ICs maybe used (e.g., Structured/Platform ASICs, an FPGA, or anothersemi-custom IC), which may be programmed in any manner known in the art.The functions of each unit may also be implemented, in whole or in part,with instructions embodied in a memory, formatted to be executed by oneor more general or application-specific processors.

All structural and functional equivalents to the elements of the variousaspects described throughout this disclosure that are known or latercome to be known to those of ordinary skill in the art are expresslyincorporated herein by reference and are intended to be encompassed bythe claims. Moreover, nothing disclosed herein is intended to bededicated to the public regardless of whether such disclosure isexplicitly recited in the claims. The words “module,” “mechanism,”“element,” “device,” “component,” and the like may not be a substitutefor the word “means.” As such, no claim element is to be construed as ameans plus function unless the element is expressly recited using thephrase “means for.”

In the appended figures, similar components or features may have thesame reference label. Further, various components of the same type maybe distinguished by following the reference label by a dash and a secondlabel that distinguishes among the similar components. If just the firstreference label is used in the specification, the description isapplicable to any one of the similar components having the same firstreference label irrespective of the second reference label.

What is claimed is:
 1. A method of wireless communication in a systemthat supports transmission time intervals (TTIs) of a first duration anda second duration that is less than the first duration, comprising:determining a hybrid automatic repeat request (HARQ) timing mode basedat least in part on one or more capabilities of a user equipment (UE) toprovide HARQ feedback in response to communications using TTIs of thesecond duration; and communicating using the HARQ timing mode.
 2. Themethod of claim 1, wherein the communicating comprises: receiving afirst transport block (TB) during a first TTI and a second TB during asecond TTI, wherein the first TTI and the second TTI each have thesecond duration; identifying a feedback time period based at least inpart on the HARQ timing mode, wherein the HARQ timing mode comprises afirst HARQ response time and a second HARQ response time that is lessthan the first HARQ response time; and transmitting one or more HARQfeedback messages associated with the first or the second TB during thefeedback time period, wherein the one or more HARQ feedback messages arereceived during a TTI of the first duration.
 3. The method of claim 1,wherein the communicating comprises: receiving a first transport block(TB) during a first TTI and a second TB during a second TTI, wherein thefirst TTI and the second TTI each have the second duration; identifyinga feedback time period based at least in part on the HARQ timing mode,wherein the HARQ timing mode comprises a first HARQ response time and asecond HARQ response time that is equal to the first HARQ response time;and transmitting one or more HARQ feedback messages associated with thefirst or the second TB during the feedback time period, wherein the oneor more HARQ feedback messages are received during a TTI of the firstduration.
 4. The method of claim 3, wherein the first TTI is within alatter part of a first time period having the first duration and thesecond TTI is within an initial part of a second time period having thefirst duration.
 5. The method of claim 3, wherein the one or more HARQfeedback messages comprise a first HARQ feedback message and a secondHARQ feedback message distinct from the first HARQ feedback message. 6.The method of claim 5, wherein a latter portion of the first HARQfeedback message and an initial portion of the second HARQ feedbackmessage are multiplexed using at least one of: a physical uplink controlchannel (PUCCH) format capable of carrying more than two bits, adivision of bits between the latter portion of the first HARQ feedbackmessage and the initial portion of the second HARQ feedback message,joint coding of one or more bits of the first HARQ feedback message andthe second HARQ feedback message, or a combination of bits based atleast in part on an orthogonal cover code (OCC) and at least one paritybit, or any combination thereof.
 7. The method of claim 1, furthercomprising: transmitting an indication of the one or more capabilitiesof the UE to a base station.
 8. The method of claim 1, furthercomprising: receiving an indication of a set of HARQ timing modes from abase station; and transmitting a HARQ timing mode request in response tothe indication, wherein the HARQ timing mode is selected from the set ofHARQ timing modes based at least in part on the HARQ timing moderequest.
 9. The method of claim 1, wherein the communicating comprises:transmitting a first transport block (TB) during a first TTI and asecond TB during a second TTI, wherein the first TTI and the second TTIeach have the second duration; identifying a feedback time period basedat least in part on the HARQ timing mode, wherein the HARQ timing modecomprises a first HARQ response time and a second HARQ response timethat is less than the first HARQ response time; and receiving one ormore HARQ feedback messages associated with the first or the second TBduring the feedback time period, wherein the one or more HARQ feedbackmessages are received during a TTI of the first duration.
 10. The methodof claim 1, wherein the communicating comprises: transmitting a firsttransport block (TB) during a first TTI and a second TB during a secondTTI, wherein the first TTI and the second TTI each have the secondduration; identifying a feedback time period based at least in part onthe HARQ timing mode, wherein the HARQ timing mode comprises a firstHARQ response time and a second HARQ response time that is equal to thefirst HARQ response time; and receiving one or more HARQ feedbackmessages associated with the first or the second TB during the feedbacktime period, wherein the one or more HARQ feedback messages are receivedduring a TTI of the first duration.
 11. The method of claim 1, furthercomprising: identifying an uplink (UL) control configuration based atleast in part on the HARQ timing mode; and transmitting an indication ofthe UL control configuration to the UE.
 12. The method of claim 1,further comprising: identifying a first physical uplink control channel(PUCCH) resource offset for UL transmissions that use TTIs of the firstduration and a second PUCCH resource offset for UL transmissions thatuse TTIs of the second duration.
 13. The method of claim 12, wherein thesecond PUCCH resource offset is identified based at least in part on thefirst PUCCH resource offset and a delta value.
 14. The method of claim12, wherein the first PUCCH resource offset or the second PUCCH resourceoffset is identified based at least in part on a PUCCH format.
 15. Themethod of claim 14, wherein the one or more resource sets for ULtransmissions are associated with each PUCCH format of a set of PUCCHformats, and wherein the one or more resource sets are each associatedwith a different base station or layer three configuration.
 16. Themethod of claim 1, further comprising: identifying a first scheduleddownlink (DL) transmission indicator associated with TTIs of the firstduration and a second scheduled DL transmission indicator associatedwith TTIs of the second duration.
 17. The method of claim 1, wherein thefirst duration is a duration of one subframe and the second duration isa duration of one slot of a subframe.
 18. The method of claim 1, furthercomprising: indicating a set of transmissions of the second durationwith a downlink assignment index (DAI).
 19. The method of claim 1,wherein the communicating using the HARQ timing mode is performed over ashared channel or a control channel.
 20. An apparatus for wirelesscommunication in a system that supports transmission time intervals(TTIs) of a first duration and a second duration that is less than thefirst duration, comprising: means for determining a hybrid automaticrepeat request (HARQ) timing mode based at least in part on one or morecapabilities of a user equipment (UE) to provide HARQ feedback inresponse to communications using TTIs of the second duration; and meansfor communicating using the HARQ timing mode.
 21. An apparatus forwireless communication in a system that supports transmission timeintervals (TTIs) of a first duration and a second duration that is lessthan the first duration, comprising: a processor; memory in electroniccommunication with the processor; and instructions stored in the memoryand operable, when executed by the processor, to cause the apparatus to:determine a hybrid automatic repeat request (HARQ) timing mode based atleast in part on one or more capabilities of a user equipment (UE) toprovide HARQ feedback in response to communications using TTIs of thesecond duration; and communicate using the HARQ timing mode.
 22. Theapparatus of claim 21, wherein the instructions causing the apparatus tocommunicate using the HARQ timing mode are further executable to:receive a first transport block (TB) during a first TTI and a second TBduring a second TTI, wherein the first TTI and the second TTI each havethe second duration; identify a feedback time period based at least inpart on the HARQ timing mode, wherein the HARQ timing mode comprises afirst HARQ response time and a second HARQ response time that is lessthan the first HARQ response time; and transmit one or more HARQfeedback messages associated with the first or the second TB during thefeedback time period, wherein the one or more HARQ feedback messages arereceived during a TTI of the first duration.
 23. The apparatus of claim21, wherein the instructions causing the apparatus to communicate usingthe HARQ timing mode are further executable to: receive a firsttransport block (TB) during a first TTI and a second TB during a secondTTI, wherein the first TTI and the second TTI each have the secondduration; identify a feedback time period based at least in part on theHARQ timing mode, wherein the HARQ timing mode comprises a first HARQresponse time and a second HARQ response time that is equal to the firstHARQ response time; and transmit one or more HARQ feedback messagesassociated with the first or the second TB during the feedback timeperiod, wherein the one or more HARQ feedback messages are receivedduring a TTI of the first duration.
 24. The apparatus of claim 23,wherein the first TTI is within a latter part of a first time periodhaving the first duration and the second TTI is within an initial partof a second time period having the first duration.
 25. The apparatus ofclaim 23, wherein the one or more HARQ feedback messages comprise afirst HARQ feedback message and a second HARQ feedback message distinctfrom the first HARQ feedback message.
 26. The apparatus of claim 25,wherein a latter portion of the first HARQ feedback message and aninitial portion of the second HARQ feedback message are multiplexedusing at least one of: a physical uplink control channel (PUCCH) formatcapable of carrying more than two bits, a division of bits between thelatter portion of the first HARQ feedback message and the initialportion of the second HARQ feedback message, joint coding of one or morebits of the first HARQ feedback message and the second HARQ feedbackmessage, or a combination of bits based at least in part on anorthogonal cover code (OCC) and at least one parity bit, or anycombination thereof.
 27. The apparatus of claim 21, wherein theinstructions are further executable by the processor to: transmit anindication of the one or more capabilities of the UE to a base station.28. The apparatus of claim 21, wherein the instructions are furtherexecutable by the processor to: receive an indication of a set of HARQtiming modes from a base station; and transmit a HARQ timing moderequest in response to the indication, wherein the HARQ timing mode isselected from the set of HARQ timing modes based at least in part on theHARQ timing mode request.
 29. The apparatus of claim 21, wherein theinstructions causing the apparatus to communicate using the HARQ timingmode are further executable to: transmit a first transport block (TB)during a first TTI and a second TB during a second TTI, wherein thefirst TTI and the second TTI each have the second duration; identify afeedback time period based at least in part on the HARQ timing mode,wherein the HARQ timing mode comprises a first HARQ response time and asecond HARQ response time that is less than the first HARQ responsetime; and receive one or more HARQ feedback messages associated with thefirst or the second TB during the feedback time period, wherein the oneor more HARQ feedback messages are received during a TTI of the firstduration.
 30. A non-transitory computer-readable medium storing code forwireless communication in a system that supports transmission timeintervals (TTIs) of a first duration and a second duration that is lessthan the first duration, the code comprising instructions executable to:determine a hybrid automatic repeat request (HARQ) timing mode based atleast in part on one or more capabilities of a user equipment (UE) toprovide HARQ feedback in response to communications using TTIs of thesecond duration; and communicate using the HARQ timing mode.